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COMFORTECH PREVIEW: How and Why to Benchmark the HVAC Systems You Service

In my high school years I worked as a surveyor. Each time we surveyed a new project, we would identify a benchmark or a reference point that all future project measurements and calculations would refer to. Let’s take a look at how you can apply this principle to add a new level of diagnostics to the HVAC systems you sell and service.

Benchmarks and Your Health
Medical professionals record your vital signs on each visit and use them as your personal benchmarks. Weight, heart rate, blood pressure, or other vital measurements are taken and recorded.

On your next checkup, the same measurements are taken and compared to previous measurements. Any changes tell a story that the doctor uses to diagnose your physical condition. Solutions are then prescribed to improve your health and increase your longevity.

Record Benchmark Readings
Just as benchmarking can be used to track your health, the same principles can be applied to an HVAC system. A few quick and simple measurements can be taken and recorded right on the equipment each time you service the system. The same measurements can be taken at any time in the future and compared to the initial benchmarked readings.

Any improvement or deterioration in the system is evident by the change in any of these measurements. You can then prescribe solutions to your customer to improve the efficiency, comfort, and longevity of each system. Invisible opportunity becomes clear for the first time.

Just like health benchmarking, these tests are simple and take only a few minutes. The hidden benefit of benchmarking is that you can begin to assess the performance of the entire system and expand your care far beyond just the mechanical equipment.

HVAC System Benchmarks
Each system comes with its own set of published benchmarks. These include rated static pressures, fan airflow, and temperatures through the system. More advanced benchmarking may include refrigerant and combustion measurements to more accurately assess the system performance.

Like the medical industry, we have published standards and specifications that determine what these benchmarks should be. We also can “read” and interpret these numbers to troubleshoot and repair any negative change in the systems we service.

Ideally, when a system is started up for the first time, and hopefully commissioned to optimize its performance, benchmark readings can be taken and recorded on a permanent label affixed to the system. This documents the ideal level of system performance and also documents that it is operating within manufacturer specifications and design intent.

If the system has never been commissioned, these readings can be taken at any time and compared to the manufacturer’s specifications or design parameters. They can then be tracked and used from that day forward to troubleshoot any negative system changes.

One interesting tip to keep in mind: we heal; HVAC systems don’t. In almost every case, deterioration is shown concretely through benchmarking which then helps you identify needed repairs and assure your customer that their system will continue to perform well.

Here’s the hard fact: Most changes that deteriorate the performance and efficiency of a system are invisible to inspection alone. You may have been missing this deterioration from the day the system was installed.

This is why the typical system delivers less than 60% of its rated heating or cooling capacity into a building. Knowing this, can you see the opportunities benchmarking can offer you, your company, and your customers?

Simple benchmarking stickers like this are very useful in establishing a baseline for measuring the health of an HVAC system

Simple benchmarking stickers like this are very useful in establishing a baseline for measuring the health of an HVAC system

For starters, let’s take a look at pressures, airflow, and temperature benchmarks. We could go deeper, but let’s stick with the basics.

Pressure
A system’s maximum-rated total external static pressure is printed right on the equipment nameplate. Record this pressure and then measure and record the actual operating suction, discharge, and total pressure on the benchmark sticker located just below the rated pressure.

If pressure decreases over time, that means either the airflow dropped, the filter was changed, or a leak developed somewhere in the duct system. This could also indicate a substantial change in the volume of outside air, if the system includes it.

Advanced pressure benchmarking may include taking pressure drops over the filter, coil, and each side of the duct system. Any change in these pressures also identifies system deterioration.

Don’t forget, each defect may be completely invisible to a typical manufacturer recommended 15-point service agreement. Basic service agreements are designed to assure the equipment outlasts the warranty period. I hope your commitment to customer comfort and efficiency exceeds the warranty of the systems you build and service.

Airflow
Measuring airflow is outside the realm of most service agreements. However, benchmarking the elements of fan airflow are not. Total external static pressure has already been recorded above, fan RPM can be measured in a minute or two.

If either of these two benchmarks changes, odds are that airflow has changed. Typically, if RPM decreases, airflow decreases, which usually indicates a reduction in the Btu delivery of the system.

Temperature
Temperature change through the system is easily measured by subtracting the difference in the air temperature entering and exiting the equipment. Understand that temperature change alone cannot be interpreted without considering airflow through the system and the operating ambient outdoor temperature.

Regarding ambient temperature and airflow, if the temperature change decreases, the performance and efficiency of the system normally decreases as well. Temperature diagnostics can be that simple.

More Opportunity in Benchmarking
Like a physician, understanding and interpreting the interactions of changes in vital signs expands and increases with more testing, study, and experience. We’ve just hit the tip of the iceberg with benchmarking in this brief article.

The scary part is that 95% of the industry misses the opportunity to effectively test and diagnose the performance of each system on tens of thousands of service calls each day. Imagine the impact on comfort and efficiency we could have if basic maintenance included a little sticker on the system and 5 minutes to record and diagnose the vital signs of the system.

Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC-based training company and membership organization. If you're an HVAC contractor or technician interested in free benchmark artwork or procedures to follow so you can gather benchmark readings, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, articles, and downloads.